linux-kernel - Re: [MM] Remove rss batching from copy_page

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Date:	Thu, 5 Nov 2009 09:27:35 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"hugh.dickins@...cali.co.uk" <hugh.dickins@...cali.co.uk>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, Tejun Heo <tj@...nel.org>
Subject: Re: [MM] Remove rss batching from copy_page_range()

On Wed, Nov 04, 2009 at 05:02:12PM -0500, Christoph Lameter wrote:
> On Wed, 4 Nov 2009, Andi Kleen wrote:
> 
> > > With per cpu counters in mm there is no need for batching
> > > mm counter updates anymore. Update counters directly while
> > > copying pages.
> >
> > Hmm, but with all the inlining with some luck the local
> > counters will be in registers. That will never be the case
> > with the per cpu counters.
> 
> The function is too big for that to occur and the counters have to be

If it's only called once then gcc doesn't care about size.

> preserved across function calls. The code is shorter with the patch
> applied:

I see. Thanks for the data.

-Andi
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